Ketones in urine in cats and dogs

What it shows

When cells cannot get enough energy from glucose — because insulin is lacking or because the animal is not eating — the body breaks down stored fat, and ketone bodies are produced (Cornell). There are three of them: acetoacetate, acetone and beta-hydroxybutyrate (BHB). The dipstick detects mainly acetoacetate, acetone much more weakly, and BHB not at all (eClinPath, Merck). If a vet wants to measure BHB, it is done in blood on a chemistry analyser or a point-of-care meter (Merck).

eClinPath notes that ketones show up in urine before they build up in blood, so urine can reveal them before the blood becomes acidic.

Higher than reference — what it may be a sign of

• Unregulated diabetes mellitus in cats and dogs (eClinPath, Merck). Ketones in urine are a sign, not a diagnosis: Cornell explains that uncontrolled diabetes can progress to ketoacidosis, which it calls a medical emergency requiring hospital care.
• Prolonged fasting or starvation, especially in young animals (eClinPath, Merck, VCA).
• Low-carbohydrate diets, which Merck lists as a cause especially in cats.
• False positives — eClinPath reports that most trace reactions are false positives and that small to moderate results can be false too. Strongly coloured urine and some substances (captopril, penicillamine, cystine) can cause them, and eClinPath recommends confirming results from small upward with another method.

Lower than reference

Negative is the expected result. Because the strip does not see BHB at all, a negative or weak strip is not the last word when a vet suspects ketosis — BHB in blood can answer that (Merck). Ketones do not have a “low” state with a meaning of its own.

Look at together with

• Blood glucose and urine glucose — ketones with high glucose point towards diabetes; ketones without them, towards fasting or diet.
• Fructosamine — the longer-term picture of blood glucose.
• Bicarbonate and blood gases — whether the blood has already become acidic.
• Blood BHB — the ketone the strip cannot see.
• Appetite and feeding — whether the animal has been eating, and what.

Units and conversion

Urine ketones on a dipstick have no unit — the result is a grade. Forms write it either in words (negative, trace, small, moderate, large) or in plus signs; eClinPath uses both side by side: trace or 1+ is about 5 mg/dL, small or 2+ about 15 mg/dL, moderate or 3+ about 50 mg/dL, and 4+ 150 mg/dL or more. The exact values depend on the strip. A grade is a guide, not an exact measurement, and no conversion applies.

Reference range

The reference range is on your lab’s form; for urine ketones it is “negative”. A trace result on its own is often a false positive, according to eClinPath, so it is read against blood and urine glucose and the animal’s condition. A clearly positive result in a cat or dog with diabetes is a reason to contact the vet promptly rather than wait for the next routine visit. The vet decides what to do next.

Cats and dogs

Sources

1. eClinPath (Cornell University) — Urinalysis: chemical constituents
2. Whitbread TJ. Urinalysis. Merck Veterinary Manual
3. Cornell Feline Health Center — Feline Diabetes
4. VCA Animal Hospitals — Urinalysis